The present invention relates to an optical mouse with scrolling function, and more particularly to an encoder wheel module and circuit board arrangement for an optical mouse.
FIGS. from 1 through 3 show an encoder wheel module and circuit board arrangement for use in an optical mouse with scrolling function. This structure of encoder wheel module and circuit board arrangement comprises a circuit board 1 having a microswitch 24, a mount 2 mounted on the circuit board 1, the mount 2 comprising two side blocks 20 at two opposite lateral sides and a wheel holder 21 raised from one side block 20, an optical encoder wheel 3 revolvably supported on the wheel holder 21 between the side blocks 20, a transmitter 22 mounted in one of the side blocks 20 and controlled by the microswitch 24 at the circuit board 1 to emit a light beam through radial slots at the optical encoder wheel 3, an optical detector 23 mounted in the other of the side blocks 20 and controlled by the microswitch 24 at the circuit board 1 to read the light beam transmitted by the transmitter 22 and to output a signal indicative of the direction and amount of rotation of the optical encoder wheel 3, and a linking mechanism 4 mounted on the mount 2 and moved with the optical encoder wheel 3 to trigger the microswitch 24 at the circuit board 1. The linking mechanism 4 is comprised of a first pressure plate 40, a second pressure plate 41, and a spring member 42. The first pressure plate 40 and the second pressure plate 41 each has a crossed profile. The first pressure plate 40 comprises a front endpiece 400 inserted into a recessed hole 210 at the wheel holder 21, two side wings 401 respectively supported on blocks 211 at two sides of the recessed hole 210, and a rear endpiece 402 connected to one end of the spring member 42. The second pressure plate 41 comprises a front endpiece 410 extended through two projecting stop wall portions 200 at one side block 20 and suspending above the microswitch 24, two side wings 411 stopped below the projecting stop wall portions 200, and a rear endpiece 412 connected to one end of the spring member 42 opposite to the rear endpiece 402 of the first pressure plate 400. When the optical encoder wheel 3 is depressed as shown in FIG. 4, the first pressure plate 40 is forced by the optical encoder wheel 3 to turn the second pressure plate 41, thereby causing the front endpiece 410 of the second pressure plate 41 to trigger the microswitch 24. This arrangement is still not satisfactory in function. The use of the linking mechanism 4 complicates the structure of the encoder wheel module and circuit board arrangement, and greatly increases its manufacturing cost. Installing the linking mechanism 4 is also not an easy job. Because the pressure plates 40 and 41 and the spring member 42 are tiny, it is difficult to accurately install the pressure plates 40 and 41 and the spring member 42 in position. During installation, the spring member 42 may be forced to jump away, or to push the second pressure plate 41 out of place. In order to hold the linking mechanism 4, the design of the mount 2 is complicated.
The present invention has been accomplished to provide an encoder wheel module and circuit board arrangement for an optical mouse, which eliminates the aforesaid drawbacks. It is one object of the present invention to provide an encoder wheel module and circuit board arrangement, which has a simple structural design. It is another object of the present invention to provide an encoder wheel module and circuit board arrangement, which is inexpensive to manufacture. According to one aspect of the present invention, the encoder wheel module and circuit board arrangement comprises a circuit board having a microswitch as the third button switch, a mount mounted on the circuit board, the mount having an integrally-formed bottom frame, an integrally-formed suspension arm spaced above the bottom frame, and an integrally-formed connecting portion connected between the bottom frame and the suspension arm at a rear side, the suspension arm having a front tongue suspending above the microswitch, an optical encoder wheel supported on the suspension arm, a transmitter mounted on the mount at one side and controlled by the circuit board to emit a light beam through radial slots at the optical encoder wheel, and an optical detector mounted on the mount at one side opposite to the transmitter and controlled by the circuit board to read the light beam transmitted by the transmitter, wherein when the optical encoder wheel is depressed, the microswitch is triggered by the front tongue of the suspension arm to accomplish third button activation. According to another aspect of the present invention, the suspension arm comprises two upright support plates disposed at two opposite sides for supporting the optical encoder wheel, the upright support plates each comprising a top V-cut and a recessed portion in the top V-cut for supporting wheel axle means of the optical encoder wheel. According to still another aspect of the present invention, the optical encoder wheel comprises a toothed disk portion at one side thereof, and the suspension arm of the mount comprises a spring plate pressed on the toothed disk portion at the optical encoder wheel to guide rotary motion of the optical encoder wheel step by step. According to still another aspect of the present invention, the suspension arm of the mount comprises two wings at two opposite sides for supporting the transmitter and the optical detector, the wings each having a plurality of through holes through which respective contact pins of the transmitter or the optical detector are extended and connected to the circuit board.